docs: def starts_within(self, start=None, end=None):
          """
          :return:  normal occurrences that start within the given start and end
          datetimes, inclusive, and drop-in occurrences that 
          """
  
          qs = self
  
          if start:
              dt_start=coerce_dt_awareness(start)
              qs = qs.filter(
                  Q(is_all_day=False, start__gte=dt_start) |
                  Q(is_all_day=True, start__gte=zero_datetime(dt_start))
              )
          if end:
              dt_end=coerce_dt_awareness(end, t=time.max)
              qs = qs.filter(
                  # Exclusive for datetime, inclusive for date.
                  Q(is_all_day=False, start__lt=dt_end) |
                  Q(is_all_day=True, start__lte=zero_datetime(dt_end))
              )
  
          return qs